Mightier Than the Sword - S3.E10

A famous author of real-life biographies of serial killers, famed for his insights, owes his success to an antique pen. He writes out his story of a serial killer's murders, then uses the pen to ""inject"" them with the story. The curse then turns the victim into a serial killer controlled by the story and forced to go out and kill. Eventually they are captured and then the author extracts the evil just as they are executed, leaving them confused and then dead. Micki becomes the author's next victim. Fortunately, Jack and Johnny stop her before she can kill anyone other than the author himself.